Chemistry 1407 Quiz 11, Fall 2017 1. What do enzymes do to the rate of a chemica

Question

Chemistry 1407 Quiz 11, Fall 2017 1. What do enzymes do to the rate of a chemical reaction? (6 points) compounds that an enryme reacts on are called. 16 points) 3. The non-protein partion of an enzyme that is necessary for an enzyme to act as a catalyst ls known as a? (6 points) A non-competitive inhibitor acts by (0) (a) binding to the active site of the enzyme b) binding to a different part of the enzyme but changing the active site of the enzyme 4. (d) none of these 5. List three (3) factors that affect enzyme activity. 19 points, 3 each) 6. Give an example of a proenzyme. (6 points) 7, Onwhat of the enyme does the substrate reaat (6 points) How can the rate of an enzymatic reaction be restored for if the reaction was slowed down by a competitive inhibitor? (6 points) 8.

Explanation / Answer

Ans. 1. Enzymes increase the rate of chemical reaction by lowering the activation energy.

#2. The compounds that an enzyme react on are called substrates.

#3. The non-protein portion of an enzyme that is necessary for an enzyme to act as catalyst is known as cofactor.

#4. Correct option. a. binding to the active site of the enzyme.

A competitive inhibitor competes with the substrate for the active site of enzyme. It so binds to the active site and thus prevents binding of substrate to enzyme’s active site. Since the inhibitor lowering the rate of substrate binding to enzyme’s active site, it lowering the rate of substrate catalysis as well as rate of product formation.

#5. Three factors affecting enzyme active-

I. Temperature: All enzymes exhibit maximum catalysis at their respective optimum temperatures. Deviation from optimum temperature (too low, too high from optimum value) lowering enzyme activity.

II. pH: All enzymes exhibit maximum catalysis at their respective optimum pH. Deviation from optimum pH (too low, too high from optimum value) lowering enzyme activity

III. Presence of Inhibitor: Presence of inhibitor always lowers the enzyme activity.

#6. Pepsinogen

Pepsinogen is a proenzyme (a catalytically inactive precursor of an enzyme) which is converted into active form “pepsin” under acidic conditions.

#7. Substrate reacts at the catalytic site (active site) of the enzyme.

#8. The reductions in rate of enzyme activity due to presence of competitive inhibitor can be restored by increasing substrate concertation.

#9. Feedback inhibition.

#10. Allosteric enzymes.

Allosteric enzymes have one or more regulatory site other than the active site. Binding of ligands, or allosteric modulators at the allosteric site regulates the catalysis at active site.

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